The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2000-155493, filed May. 25, 2000.
1. Field of the Invention
The present invention relates to a shape measurement device for an article whose shape is required to be accurate, and in particular relates to a shape measurement device intended for the measurement of a carrier which is used upon a semiconductor device production line for transporting a set of several semiconductor wafers all together.
2. Description of the Related Art
Upon a production line for semiconductor devices, in order to transport a semiconductor wafer between devices which perform film deposition, processing or the like, there has been employed a per se known method of transporting the semiconductor wafers by collecting together several at one time in a receptacle termed a xe2x80x9ccarrierxe2x80x9d. Generally, this type of carrier is formed with a number of slots being provided upon its inner walls on both its sides at predetermined intervals, and is made so as to hold a plurality of semiconductor wafers in a horizontally superimposed state with predetermined intervals between them, by supporting both the sides of the semiconductor wafers by these grooves.
When a semiconductor wafer is to be taken out from the carrier after it has been transported and is to be inserted into a device which performs a process like film deposition, processing or the like, a so called xe2x80x9crobot armxe2x80x9d device inserts the end of an arm, which is formed in a thin plate shape, between two adjacent semiconductor wafers in the carrier. Then the end of the robot arm performs the operation of pulling a single semiconductor wafer out forwards towards itself along the grooves while lifting it up by its under surface.
At this time there is a danger that, if the space between one semiconductor wafer and the adjacent one supported in the carrier deviates from its design value by more than its permitted value, the end of the robot arm may touch against the upper surface of the adjacent semiconductor wafer. Since film deposition, processing or the like has been performed upon the upper surfaces of the semiconductor wafers by the previous processes up until this point, it is not desirable for the end of the robot arm to come into contact with any upper wafer surface, because damage or contamination may result. Furthermore, if the heights at which the semiconductor wafers are supported in the carrier deviate from the design values, apart from the possibility that the robot arm may touch the upper surface of some semiconductor wafer, there is a danger that one semiconductor wafer may be damaged by collision with the front edge of the semiconductor wafer. Yet further, if one of the semiconductor wafers is tilted, the end of the robot arm may not be able properly to lift up this semiconductor wafer. Due to these problems, it is extremely important for the heights at which the semiconductor wafers are supported in the carrier, the spaces between the semiconductor wafers, and the inclinations of the semiconductor wafers, all to be constrained to be within their permitted ranges around their design values.
For this reason, a shape measurement operation is performed at the time of shipping of the carrier from the carrier manufacturer and/or at the time of receipt of the carrier by the semiconductor device maker, in order to determine whether or not the shape of the carrier accords with its design values. Further, it may happen that the carrier becomes deformed during use, since cleansing processes and the like upon a semiconductor device production line are performed at high temperatures. Due to this, a measurement operation may be performed by the semiconductor device maker while the carrier is partway along the production line, in order to check whether or not its shape accords with its design values.
There is a per se known prior art carrier shape measurement device which measures the shape of a so called open carrier in which apertures are formed both in its front surface and also in its rear surface. With this structure, this open carrier is illuminated from its rear, and images are formed by a CCD camera or the like of the external shape of the carrier and the shapes of the grooves from the front, and the process of shape measurement is performed by processing these images.
However, since the grooves in the carrier are formed upon both the sides thereof, even if the shapes of these grooves are measured, it has been difficult accurately to derive from these values the spaces between the central portions of the wafers which are supported in these grooves, and their heights and inclinations. In particular, with a carrier shape measurement device according to this prior art, since the images which are used are formed from the front side of the carrier, therefore information cannot be obtained as to what the shapes of the grooves may be, further in the direction into the grooves than the depth of focus of the CCD camera. Because of this, even though the spaces between the wafers which are supported in these grooves, and their heights and inclinations, can be derived with accuracies on the order of millimeters, there have been great difficulties in increasing the accuracy above such a level.
More particularly, in recent years, the use has increased of so called large size semiconductor wafers of diameter of 300 mm or greater. Since both the edges of these large size semiconductor wafers are supported in the carrier in grooves which are several millimeters deep, it becomes more and more difficult to know, from the shapes of the grooves, the state of support with regard to the spaces between the central portions of the wafers and their inclinations and the like. Moreover since, in the case of semiconductor wafers of large diameter, if a wafer is inclined even a little, the spaces between it and the neighboring wafers become extremely restricted, therefore a measurement accuracy on the order of millimeters is no longer adequate, and a further enhancement of the accuracy of measurement is desirable.
Yet further, since such a carrier measurement device according to the prior art is directed towards measurement of an open carrier, therefore it is not capable of being applied to the measurement of the shape of a sealed type carrier which has a blocked rear side and a cover over its front side, such as a so-called FOUP (Front Opening Unified Pod) carrier for wafers of 300 mm diameter according to the SEMI standard.
The objective of the present invention is to propose a carrier shape measurement device which can measure with high accuracy the attitudes of semiconductor wafers which are loaded into the carrier.
In order to attain the above described objective, a shape measurement device according to the present invention, comprises: a stage for loading a subject for measurement; an imaging section that forms an image of the subject for measurement; and a shifting section that implements relative shifting between the imaging section and the subject for measurement to shift the imaging section to a position corresponding to a portion on the subject for measurement which is to be measured, and the shifting section implements the relative shifting by shifting the imaging section without shifting the stage.
Another shape measurement device according to the present invention, comprises: a stage for loading a subject for measurement; a measurement section that measures a shape of the subject for measurement; a shifting section that implements relative shifting between the imaging section and the subject for measurement to shift the imaging section to a position corresponding to a portion on the subject for measurement which is to be measured; and a chassis that houses at least a part of the measurement section and the shifting section. And: the chassis is formed, at a region thereof which faces the subject for measurement, with an aperture which does not hinder the shifting of the measurement section; an end of the measurement section protrudes from the aperture towards the subject for measurement; and a dustproof member is disposed at the aperture in order to prevent dust within the chassis from leaking out towards the subject for measurement while not hindering the shifting of the measurement section, the dustproof member covering the aperture except for a portion corresponding to the measurement section.
In this shape measurement device, it is preferred that a negative pressure device that decompresses an interior of the chassis in order to distort the dustproof member and create an air current which enters into the chassis through a gap between the distorted dustproof member and the aperture, is further provided.
Another shape measurement device according to the present invention, comprises: a stage for loading a subject for measurement; a measurement section that measures a shape of the subject for measurement; and a shifting section that implements relative shifting between the measurement section and the subject for measurement to shift the measurement section to a position corresponding to a portion on the subject for measurement which is to be measured. And the measurement section comprises an illumination section which illuminates laser light upon the subject for measurement from a slanting direction, a light reception section which receives the laser light which has been reflected from the subject for measurement, and a rotation drive section which rotates the illumination section and the light reception section while preserving a mutual positional relationship of the illumination section and the light reception section, without changing a region upon the subject for measurement which is illuminated by the laser light.
In this shape measurement device, it is preferred that the measurement section comprises an imaging section for forming an image of the subject for measurement, and detects a distance from the subject for measurement along a direction of an optical axis of the imaging section based upon an output from the light reception section.